Method for automatically controlling a transmission brake of an automatic transmission configured as a countershaft transmission

ABSTRACT

A method for controlling and regulating a transmission brake of an automatic transmission designed as a gear reduction unit in which the rotation speed of a countershaft of the gearbox can be decelerated in an upshift such that it corresponds to the synchronized rotation speed or comes close to it up to a predetermined distance during an upshift operation. The brake gradient of the countershaft rotation speed or the gear input rotation speed as well as the gear output shaft rotation speed is taken into consideration for the control and regulation of the gearbox brake. To improve the upshifts, operations it is provided that for the control and the regulation of the gearbox brake, in addition, the gradient of the gear output shaft rotation speed is analyzed.

The invention relates to a method for controlling and regulating the operation of a gearbox brake of an automatic transmission designed as a gear reduction unit according to the preamble of claim 1.

It is generally known that manual and automatic transmissions usually comprise an input shaft, an output shaft that is coaxial to the input shaft and a countershaft. Depending on the number of gears, there is a corresponding number of gear wheels on the gear shafts, on which there is a stationary wheel mounted on a gear shaft combs with at least one loose wheel arranged on a further gear shaft.

With a forward shift generally one of the loose wheels will be non-rotatably connected to the gear shaft via a positively acting clutch arrangement, which transmits the total drive torque. In order to transmit large torque with simple, space-saving and easily switched means, one preferably uses positive clutches. During the forward gearshift the tractive power of the driving engine will, however, be interrupted by way of a special switching and starting clutch.

In order to shift such transmissions easily, lightly, jerk-free, quickly and with low noise, the switching parts of the clutch arrangement must have about the same number of revolutions before these mesh with one another. For this purpose, synchronizing parts are provided, which delay or accelerate the drive-side part of the drive train between the shifting and starting clutch and clutch arrangement that is supposed to be shifted during a tractive power interruption phase to a speed that is set depending on the driving speed and the gear ratio of the target gear. If one switches from a lower gear to a higher gear then with the help of the synchronization arrangement the drive-side part of the gearbox will be delayed, whereas it will be accelerated in a reverse gear motion.

The ordinary synchronization arrangements have for these delayed and accelerated actions, friction clutches in the form of friction cones. These do not have to transmit the entire torque, but only perform the synchronization work, which is a result of the moments of inertia of the rotating masses of the drive-side part of the transmission as well as the friction-related drag torque. Therefore they can accordingly be made of a small dimension.

Typically each of the positive clutch arrangements is provided with a synchronization arrangement. It is, however, also possible that a central synchronization arrangement assumes the synchronizing work for several or all positive clutch arrangements.

In order to relieve the driver of a vehicle from the mechanical shift and clutch processes associated with shifting operations, these automated shifting processes are performed by auxiliary force-aided adjusting controls in automated gearboxes, which are selected by a controlling and regulation arrangement.

In addition, such a controlling and regulation arrangement uses vehicle sensor data to detect the driver's preferences and controls and regulates the switching activity of the gearbox on their basis by way of memorized controlling and regulation programs.

In such automatic gearboxes, the synchronization process can, for example, be controlled and regulated so that during reverse control operations the number of rotations of the gear input shaft or the countershaft will be raised due to the increase in the engine speed whereas during up-shifts these drive-side shafts of the gearbox will be decelerated. In order to carry out such brake activities, there are centrally synchronized gearboxes, which usually are coupled via a gearbox brake that is connected to the counter shaft. Such gearbox brakes can be operated electrically, hydraulically or pneumatically, whereby the latter operating mechanism is more often used for commercial vehicle gearboxes.

In DE 196 52 916 Al an automatic transmission with a hydraulically or pneumatically operated gearbox brake is known wherein on the latter a countershaft can act. The pressure fluid control valves of the gearbox brake are controlled by a microprocessor dependent on the desired type of switch and the other driving conditions.

If a higher gear is, for example, chosen and the countershaft must be decelerated for synchronization, the microprocessor will calculate a target revolution speed (synchronized revolution speed) for the countershaft based on the chosen gear transmission ratio and by way of a sensor, wherein mechanic coupling of the target gear loose wheel can occur when said target speed has been reached.

Due to the usually difficult to regulate air pressure as well as other varying surrounding conditions, the brake power of the gearbox brake is subjected to large fluctuations. In order to achieve the necessary rotation speed, that is the maximum distance of the actual rotation speed of the gear input shaft or that of a countershaft driven by it to the target rotation speed for the concrete switch activity, according to the state of the art, the braking gradient is determined and taken into consideration by the microprocessor during the control of the gearbox brake. For this to happen, the microprocessor regulates the control valves in such a way that the known preset given values and thus the synchronized rotation speed for engagement of the clutch arrangement on the respective loose wheel can be reached.

Unfortunately, the synchronous rotation speed is not a set speed for a switch activity and is among other things dependent on the grade of the road. The reason for this is that a switch activity with an open starting and switching clutch as well as a grade can lead to a negative vehicle acceleration and thus to a decline in the gear output speed and for a gradient when the gearbox brake is not being operated it could lead to a positive vehicle acceleration. These influences have not been accounted for previously in the state of the art for the control and regulation methods for gearbox brakes, which means that before their means of operation was not complete.

The task of the invention is therefore to continue to improve the control and regulation of the gearbox brake.

The solution to this task is found in the features of the main claim, while the inventive advantages of further development and design are found in the subordinate claims.

The invention concerns the control and regulation of the gearbox brake of an automatic transmission designed as a gear reduction unit, which consists of a gear input shaft, at least one countershaft driven by the gear input shaft and a gear output gear shaft. The gear input gear shaft is connected to a drive shaft of a drive motor via a starting and shifting clutch, while the gear output gear shaft is connected via at least one differential gearbox to drive shafts connected to the vehicle wheels. On the gear input shaft, on countershaft or countershafts and/or on the gear output shaft, cog wheels are arranged non-rotatably, which mesh with each other at least in pairs. In addition such a gearbox has positive clutch arrangements that aid the loose wheels in being non-rotatably connected to the gear shaft alternatively to each other when carrying out a gearshift.

In addition such a gearbox is equipped with a gearbox brake as well as a control apparatus to at least technically connect the gearbox brake with a signal. With the aid of the gearbox brake at least one of the countershafts can be decelerated in an upshift process such that its rotational speed corresponds to the synchronized engine speed at the engagement time or it gets close to a predetermined distance. In that case in the control and regulation of the transmission brake, the brake gradient of the gear reduction unit and respectively the gear input shaft rotation speed as well as the gear output shaft rotation speed will be considered.

In order to improve a transmission upshift process, the invention has provided that in addition to the above-mentioned variables for the control and regulation of the transmission brake the gradient of the gear output shaft rotation speed also is analyzed. Using this method, the gear output shaft speed will be linked to the speed of the countershaft with the gear ratio of the target speed and also environmental and/or road conditions will be able to be taken into consideration better. In particular, during the shifting operation, quick changes in the gear output shaft speed can be taken into consideration for the control and regulation of the transmission brake.

In a preferable arrangement of the invention, it is foreseen that the gradient of the gear input shaft speed or the countershaft speed and the gradient of the gear output shaft speed reach a total gradient. This total gradient can then be used to calculate the shutdown time of the transmission brake when reaching the synchronization time. The shutdown time can, therefore, also be determined for variable transmission brake friction values and changing output rotation speed gradients to secure a safe and fast shifting operation without jerks.

The connections of the control and regulation method, according to the invention, to mathematics and physics, as well as the equations based on this are derived from the drawing and explained in the following. In this drawing, the engine speed gradients of the target speed (n_(Soll)) and the actual speed (n_(lst)) of the gear input shaft or the countershaft during a downshift operation before and after reaching the synchronized time (t_(s)) are depicted. Here the synchronized time is defined as the time in which the target and actual gradients of the gear input shaft or countershaft speed intersection one another. As the gear input shaft usually drives the countershaft of the transmission, via a stationary wheel toothing, the rotation speeds of the gear input shaft and countershaft are proportional to one another so that it makes no difference whether the gear input shaft rotation speed or the countershaft rotation speed is used for controlling and regulating the transmission brake.

Although the inventive method concerns the deceleration of the transmission shaft during an upshift operation, the fundamental connections during a transmission shifting operation can also be understood from this diagram.

For the rotation speed difference Δn_(i) between the target rotation speed n_(Soll) and the actual rotation speed n_(lst) of the gear input shaft or countershaft at the time t_(i) the following applies: Δn _(i) =n _(Soll) −n _(lst)   (G1.1) as well as for the above-mentioned rotation speed gradients with t_(p) representing the predetermined scanning or program cycle time. $\begin{matrix} {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - {\Delta\quad n_{i - 1}}}{t_{p}}} & \left( {{G1}{.2}} \right) \end{matrix}$

The rotation speed difference Δn between the target rotation speed n_(Soll) and the actual rotation speed n_(lst) of the gear input shaft or countershaft accordingly during the time frame I before the synchronization time I_(s) for a down-shift is Δn_(i)>0, while for an up-shift it is n_(Soll)<n_(lst)

Δn_(i)<0.

According to the following equation, the value for the rotation speed total gradient Δ{dot over (n)} during a down-shift is: |Δn _(i) |<|Δn _(i−1)|

{dot over (n)}<0   (G1.3) and during an upshift it is: |−Δn _(i) |<|−Δn _(i)−1|

{dot over (n)}>0   (G1.4)

For the rotation speed ratios during the time I I after the synchronized time frame I_(s) the following equations apply: Δn _(i)<0 (n _(Soll) <n _(lst))   (G1.5) in the case of a downshift and Δn_(i)>0   (G1.6) for an upshift.

Therefore the rotation speed total gradient Δ{dot over (n)} has the following value when there is a downshift operation in the time I I after the synchronized time I_(s): |−Δn _(i) <|−Δn _(i)−1|

{dot over (n)}<0   (G1.7) and in the case of an upshift |Δn _(i) |<|Δn _(i−1)|

{dot over (n)}>0   (G1.3)

The synchronization time Is can be calculated from the quotient of the rotation speed difference Δn_(i) between the target rotation speed n_(Soll) and the actual rotation speed n_(lst) of the gear input shaft or countershaft and the rotation speed gradient {dot over (n)} so that the following equation applies for the synchronization time: $\begin{matrix} {t_{s} = \frac{\Delta\quad n}{\overset{.}{n}}} & \left( {{G1}{.9}} \right) \end{matrix}$

A change to temporally discrete steps results in the following rotation total gradient for the programming of the control and regulation apparatus for the rotation speed gradient {dot over (n)}: $\begin{matrix} {\frac{\Delta\quad n_{i}}{\Delta\quad n_{i - 1}} = {\left. \frac{t_{Si}}{t_{{Si} - 1}}\Rightarrow\overset{.}{n} \right. = {\frac{\Delta\quad n_{i}}{t_{Si}} = \frac{\Delta\quad n_{i - 1}}{t_{{Si} - 1}}}}} & \left( {{G1}{.10}} \right) \end{matrix}$ in which t_(Si) is the time frame from the time t_(i) until the synchronization time t_(S).

By changing the equation (GI.10) by using equation (G1.2) one arrives at the following equation: $\begin{matrix} {t_{p} = {{t_{Si} - t_{{Si} - 1}} = {{\frac{\Delta\quad n_{i}}{\overset{.}{n}} - \frac{\Delta\quad n_{i - 1}}{\overset{.}{n}}} = \frac{{\Delta\quad n_{i}} - {\Delta\quad n_{i - 1}}}{\overset{.}{n}}}}} & \left( {{G1}{.11}} \right) \end{matrix}$ that can be modified into the equation for the rotation speed total gradient {dot over (n)} $\begin{matrix} {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - {\Delta\quad n_{i - 1}}}{t_{p}}} & \left( {{G1}{.12}} \right) \end{matrix}$ Here with concrete programming a program cycle time t_(p) of preferably 10 ms can be planned. In such a case the rotation speed total gradient {dot over (n)} is at t_(p)=10 ms, which is equal to a value of t_(p)=1, on with an overlapping calculation at t_(p)=20 ms leads to a value t_(p)=2.

In addition, the time frame t_(Si) from the time t_(i) until the synchronization time t_(S) is found on the basis of the following equation $\begin{matrix} {t_{Si} = {\frac{\Delta\quad n_{i}}{\overset{.}{n}} = {k*t_{p}}}} & \left( {{G1}{.13}} \right) \end{matrix}$ in which k is the number of program cycles until the synchronization time t_(S) is reached.

The concrete steps of completing such a control program sequence preferably follow the following sequence of events:

-   a. Establishing the rotation speed difference Δn_(i) between the     target and actual rotation speeds at time t_(i):     Δn=(n _(Soll) −n _(lst))   (G1.14) -   b. Overlapping calculation of the rotation speed gradient with a     program cycle time t_(p)=20 ms: $\begin{matrix}     {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - n_{i - 2}}{2}} & \left( {{G1}{.15}} \right)     \end{matrix}$ -   b. Intermediate storage of the rotation speed differences for the     next calculation:     Δn _(i−2) =Δn _(i−1)   (G1.16)     Δn _(i−1) =Δn _(i)   (G1.17) -   d. Calculation of the time until the synchronization time t_(S) as     well as the necessary program cycles have been reached:     $\begin{matrix}     {t_{Si} = \left. \frac{\Delta\quad n_{i}}{\overset{.}{n}}\rightarrow{k*t_{p}} \right.} & \left( {{G1}{.18}} \right)     \end{matrix}$ -   e. actuation of the transmission brake until reaching the     synchronization time t_(S) or a predetermined distance to this     synchronization time t_(S).

REFERENCE NUMERALS

-   n rotation speed -   n_(Soll) target rotation speed of the countershaft or the gear input     shaft during shifts -   n_(lst) actual rotation speed of the countershaft or the gear input     shaft during shifts -   n_(i) the rotation speed at the time t_(i) -   Δn_(i) the rotational speed difference between the target and the     actual rotation speed at time t_(i) -   t time -   t_(i) time frame -   t_(p) program cycle time -   t_(S) time at which the target and actual rotation speed courses     intersect one another (synchronization time) -   t_(Si) time between time t_(i) and synchronization point t_(S) -   {dot over (n)} rotational speed total gradient 

1-6. (canceled)
 7. A method for controlling and regulating a transmission brake of an automatic gearbox designed as a gear reduction unit, with a gear input shaft, with at least one countershaft that can be driven by the gear input shaft and with a gear output shaft, on which loose cog wheels are seated on the gear input shaft, on the countershaft and/or on the gear output shaft and/or having loose rotational cog wheels seated non-rotatably and/or stationary cog wheels seated non-rotatably, which at least form pairs in tooth engagement with one another, whereby the loose wheels are connected non-rotatably to the gear shaft by means of the clutch arrangements to be able to perform a gearshift, as well as with a transmission brake and a control apparatus for controlling and regulating at least this transmission brake, with which the countershaft can be decelerated during an upshift, that the rotation speed until the coupling time corresponds to the synchronized rotation speed or is close to a predetermined distance, whereby the control and regulation of the transmission brake takes the brake gradient of the countershaft speed or the gear input shaft rotation speed as well as the gear output shaft rotation speed into consideration, wherein for the control and regulation of the transmission brake additionally the gradient and the gear output shaft rotation speed is analyzed.
 8. The method according to claim 7, wherein from the gradient of the countershaft or the gear input shaft rotation speed and the gradient of the gear output shaft rotation speed a total gradient speed is calculated.
 9. The method according to claim 8, wherein the rotation speed total gradient {dot over (n)} can be calculated based on the following equation $\begin{matrix} {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - {\Delta\quad n_{i - 1}}}{t_{p}}} & \left( {{G1}{.19}} \right) \end{matrix}$ in which t_(p) represents the program cycle time and Δn_(i) the rotation speed difference between the target and actual rotation speed of the countershaft or gear input shaft rotation speed at time t_(i).
 10. The method according to claim 7, wherein the shutdown time for the transmission brake is determined from the rotation speed total gradient {dot over (n)} in order to reach the synchronized rotation speed.
 11. The method according to claim 10, wherein the shutdown time frame until reaching the synchronized rotation speed can be calculated by the following equation: $\begin{matrix} {t_{Si} = {\frac{\Delta\quad n_{i}}{\overset{.}{n}} = {k*t_{p}}}} & \left( {{G1}{.20}} \right) \end{matrix}$ in which k depicts the number of program cycles.
 12. The method according to at claim 7, wherein a program for a control and regulation apparatus that triggers the transmission brake comprises the following steps: forming the rotation speed difference Δn_(i) between the target and actual rotation speed at the time t₁: Δn=(n _(Soll) −n _(lst))   (G1.21) overlapping calculation of the rotation speed total gradient: $\begin{matrix} {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - n_{i - 2}}{2}} & \left( {{G1}{.22}} \right) \end{matrix}$ intermediate storage of the rotation speed difference for the following calculation activity: Δn _(i−2) =Δn _(i−1)   (G1.23) Δn _(i−1) =Δn _(i)   (G1.24) calculation of the time frame until the synchronization time and the calculation of the number of program cycles: $\begin{matrix} {t_{Si} = \left. \frac{\Delta\quad n_{i}}{\overset{.}{n}}\rightarrow{k*t_{p}} \right.} & \left( {{G1}{.25}} \right) \end{matrix}$ and actuating of the transmission brake until the synchronization time t_(S) has been reached or a predetermined distance to the synchronization time t_(S).
 13. A method for controlling and regulating a transmission brake of an automatic gearbox having a gear input shaft, a gear output shaft and at least one countershaft that can be driven by the gear input shaft, the method comprising the steps of seating cog wheels on one or more of the countershaft, the gear output shaft and the gear input shaft, the cog wheels are one of loose rotational cog wheels non-rotatably seated or stationary cog wheels non-rotatably seated and are, in pairs, in tooth engagement with one another, connecting the loose wheels, non-rotatably, to the gear shaft through clutch arrangements in order to perform a gearshift, connecting the loose wheels with a transmission brake and a control apparatus for controlling and regulating at least this transmission brake to decelerate the countershaft during an upshift such that the rotation speed, until a coupling time, corresponds to a synchronized rotation speed or is close to a predetermined distance, considering one of a brake gradient of the countershaft speed or the gear input shaft rotation speed and the gear output shaft rotation speed when controlling and regulating the transmission brake, additionally analyzing the brake gradient and the gear output shaft rotation speed to control and regulate the transmission brake.
 14. The method according to claim 13, further comprising the step of calculating a total gradient speed from one or more of the gradient of the countershaft, the gear input shaft rotation speed and the gradient of the gear output shaft rotation speed.
 15. The method according to claim 14, further comprising the step of calculating the rotation speed total gradient {dot over (n)} based on the following equation $\begin{matrix} {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - {\Delta\quad n_{i - 1}}}{t_{p}}} & \left( {{G1}{.19}} \right) \end{matrix}$ in which t_(p) represents a program cycle time and Δn_(i) represents a rotation speed difference between a target and actual rotation speed of one of the countershaft or gear input shaft rotation speed at time t_(i).
 16. The method according to claim 13, further comprising the step of determining a shutdown time frame for the transmission brake from the rotation speed total gradient {dot over (n)} in order to reach the synchronized rotation speed.
 17. The method according to claim 16, further comprising the step of calculating the shutdown time frame until reaching the synchronized rotation speed using the equation: $\begin{matrix} {t_{Si} = {\frac{\Delta\quad n_{i}}{\overset{.}{n}} = {k*t_{p}}}} & \left( {{G1}{.20}} \right) \end{matrix}$ in which k is a number of program cycles.
 18. The method according to claim 13, further comprising a method triggering the transmission brake with a program for a control and regulation apparatus comprises the steps of: forming the rotation speed difference Δn_(i) between the target and actual rotation speed at the time t₁: Δn=(n _(Soll) −n _(lst))   (G1.21) overlapping calculation of the rotation speed total gradient: $\begin{matrix} {\overset{.}{n} = \frac{{\Delta\quad n_{i}} - n_{i - 2}}{2}} & \left( {{G1}{.22}} \right) \end{matrix}$ intermediately storing the rotation speed difference for the following calculation activity: Δn _(i−2) =Δn _(i−1)   (G1.23) Δn _(t−1) =Δn _(i)   (G1.24) calculating the time frame until the synchronization time and the calculation of the number of program cycles: $\begin{matrix} {t_{Si} = \left. \frac{\Delta\quad n_{i}}{\overset{.}{n}}\rightarrow{k*t_{p}} \right.} & \left( {{G1}{.25}} \right) \end{matrix}$ and actuating the transmission brake until one of the synchronization time t_(S) or a predetermined distance to the synchronization time t_(S) has been reached. 